IsAlpha function not accepting my input.

[deathslice]

So the purpose of the isalpha function is that it only accepts letters(a-z) but that doesn't seem to be the case for my code. If I input the letter p, the error message is displayed. If input a word like "city", the error message is still displayed. What's wrong with my code.

#include <iostream>
#include <string>
#include <cctype>

using namespace std;

int main()
{
    const int SIZE = 10;
    char letter[SIZE];

    cout << "Enter a word. ";
    cin.getline(letter, SIZE, '\n');

    while(!isalpha(letter[SIZE]))
    {
        cerr << "Error, only letters are allowed. ";
        cin.getline(letter, SIZE, '\n');
    }

    cout << "This is acceptable. ";

    return 0;
}

#include <iostream>
#include <string>
#include <cctype>

using namespace std;

int main()
{
    const int SIZE = 10;
    char letter[SIZE];

    cout << "Enter a word. ";
    cin >> letter[SIZE];

    while(!isalpha(letter[SIZE]))
    {
        cerr << "Error, only letters are allowed. ";
        cin >> letter[SIZE];
    }

    cout << "This is acceptable. ";

    return 0;

[deathslice]

So for some reason the second piece of code works but the first one constantly loops the error message no matter what. Can someone please explain?

[swp147]

isalpha() only tests a single char.

Line 15 only tests letter[10] which is only one element.

i.e. letter[] = "hello",
letter[0] = 'h'
letter[1] = 'e'
letter[2] = 'l'
letter[3] = 'l'
letter[4] = 'o'
letter[5] = '\0'; (string terminator)

Testing isalpha[4] would be true, isalpha[5] would be false (its not a letter, its \0)

[deathslice]

I see, so there is any other way to test if each element is a letter. Sorry if I'm responding so late.

[swp147]

Well, in C, you have to walk through the whole string and test each element separately. C++ might have a string method to determine this, but this is probably just as easy.